Greases containing twelve-hydroxy calcium stearate, and processes for their preparation, are well known to those skilled in the art.
In 1953, in their U.S. Pat. No. 2,822,331, John P. Dilworth et al. disclosed (at column 1) that prior art " . . . attempts to make a substantially anhydrous calcium 12-hydroxy grease by conventional grease making procedures have proved unsatisfactory due to the fact that the resulting product is so grainy and has such poor stability as to be unsalable". This patent disclosed a composition containing minor amounts of the estolide polyesters of 12-hydroxy stearic acid.
In 1966, the problems with the manufacture of calcium hydroxy stearate greases were again discussed. In their U.S. Pat. No. 3,242,083, Crookshank et al. disclosed (at column 1) that "Calcium hydroxy fatty acid soap thickened greases are very difficult to prepare in satisfactory smooth form by the low temperature process of the prior art, due to the tendency of these greases to form lumpy or grainy products. Very close control of the operating conditions is therefore required in the preparation of these greases. In addition, the low temperature methods of the prior art have the serious economic disadvantage of requiring very long manufacturing times".
In 1958, in their U.S. Pat. No. 2,841,556, Reuben A. Swenson et al. disclosed (at column 1) that ". . . the prior art method of preparing calcium soap greases with 12-hydroxy stearic acid requires slow, careful dehydration at temperatures below about 275 F. over a relatively long period of time. One method of preparing such . . . greases . . . requires about 14 hours for dehydration".
These prior art 12-hydroxy calcium stearate greases, although satisfactory for certain purposes, often exhibited poor oxidation resistance, and/or poor compatibility with elastomeric materials.
It is an object of this invention to provide a process for preparing a 12-hydroxy calcium stearate grease with improved oxidation resistance.
It is another object of this invention to provide a process for preparing a 12-hydroxy calcium stearate grease with improved compatibility with elastomeric materials.
It is yet another object of this invention to provide a process for preparing a 12-hydroxy calcium stearate grease with improved uniformity.
It is yet another object of this invention to provide a process for the preparation of a 12-hydroxy calcium stearate grease which requires less energy than comparable prior art processes.
It is yet another object of this invention to provide a process for the preparation of a 12-hydroxy calcium stearate grease with a substantially higher yield of the desired product.
It is yet another object of this invention to provide a process for the preparation of a 12-hydroxy calcium stearate grease which produces a product with improved stability when subjected to shear.